A method for regenerating and remediating graphite waste residue after wet lithium extraction from spent lithium batteries.

Abstract

This invention discloses a method for regenerating and remediating graphite waste residue after wet lithium extraction from spent lithium batteries, relating to the field of solid waste recycling technology. The invention proposes a combined treatment technique involving mixing with an inorganic strong alkali or carbonate, heat treatment, high-pressure acid leaching, slurry preparation, and spiral separation. This technique significantly reduces the ash and impurity content in the lithium-extracted graphite, particularly effectively removing impurities such as ZrO2 and TiO2, resulting in high-purity graphite. The obtained high-purity graphite is then mixed with a coating agent and subjected to carbonization treatment, optimizing the microstructure and specific surface area of ​​the graphite material, ultimately yielding high-purity, high-capacity, and high-efficiency lithium-ion battery anode graphite material.

Description

Technical Field

[0001] This invention relates to the field of solid waste recycling technology, and more specifically, to a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries. Background Technology

[0002] The development of new energy electric vehicles (EVs) and the electronics industry generates a large number of waste lithium-ion batteries. Effective recycling of these batteries can prevent environmental pollution and conserve valuable resources. Currently, research on the recycling of waste lithium-ion batteries mainly focuses on pyrometallurgy and hydrometallurgy, with little research on the recycling of complete parts and components, especially the recycling of graphite after hydrometallurgical lithium extraction from waste lithium batteries, for which there is a lack of effective and cost-efficient methods. With the accumulation of waste lithium-ion batteries and energy shortages, the recycling of graphite is receiving increasing attention. However, despite reports of various methods, the recycled graphite cannot meet the stringent commercial standards for purity, efficiency, and capacity.

[0003] Graphite waste residue after recovering high-value metals using lithium extraction methods such as acid leaching and extraction not only contains small amounts of cathode materials, electrolyte, and heavy metals, but also often contains trace amounts of metal oxides such as ZrO2, TiO2, and Al2O3. These oxides remain in the graphite waste residue after acid leaching and extraction (ZrO2 and TiO2, due to their extremely high chemical stability, cannot be effectively removed by conventional acid and alkali leaching methods), posing significant challenges to the purification and remediation of the graphite waste residue. Furthermore, the graphite waste residue contains some conductive carbon black and binders such as SBR, PVDF, and CMC. If mixed with graphite, this not only affects the graphite's capacity but also reduces its BET (Best Before Equivalent) value, thereby increasing its irreversible capacity and lowering its initial coulombic efficiency.

[0004] Therefore, there is an urgent need to provide a short-process and easy-to-operate method to treat graphite waste residue after lithium extraction in order to obtain high-performance anode graphite materials that can achieve both high purity, high capacity and high initial efficiency.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries. The aim is to provide a short-process and easy-to-operate method to treat the graphite waste residue after lithium extraction in order to obtain high-purity graphite.

[0007] This invention is implemented as follows:

[0008] In a first aspect, the present invention provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, comprising:

[0009] The graphite waste residue is mixed with an inorganic strong alkali or carbonate, and then subjected to heat treatment to obtain the first graphite material.

[0010] The first graphite material is mixed with a treatment solution containing inorganic acid and oxidant, subjected to high-pressure acid leaching, and then separated into solid and liquid components to obtain the second graphite material.

[0011] The second graphite material is mixed with water to form a slurry, thus obtaining a graphite slurry.

[0012] The graphite slurry was fed into a spiral centrifuge for centrifugal separation to obtain the third graphite material.

[0013] In an optional embodiment, during the preparation of the first graphite material, the heat treatment temperature is 800℃-1200℃, and the holding time is 2h-10h.

[0014] And / or, heat treatment is performed under an inert atmosphere.

[0015] In an optional embodiment, the inorganic strong base is selected from at least one of sodium hydroxide and potassium hydroxide, and the mass ratio of graphite waste residue to inorganic strong base is 100:(3-10).

[0016] And / or, the carbonate is selected from at least one of sodium carbonate and potassium carbonate, and the mass ratio of graphite waste residue to carbonate is 100:(3-10);

[0017] And / or, first dry the graphite waste residue and then mix it with an inorganic strong alkali or carbonate, controlling the drying temperature at 80℃-200℃ and the drying time at 10h-30h.

[0018] In an optional embodiment, during the preparation of the second graphite material, the high-pressure acid leaching reaction temperature is 110℃-180℃, the reaction pressure is 1MPa-2MPa, and the reaction time is 60min-36h. After that, the temperature is reduced and the pressure is released before solid-liquid separation is performed.

[0019] And / or, the inorganic acid in the treatment solution is selected from at least one of sulfuric acid, hydrochloric acid and nitric acid.

[0020] In an optional embodiment, the inorganic acid in the treatment solution is a mixed acid, and the mixed acid includes sulfuric acid;

[0021] And / or, the oxidant in the treatment solution is hydrogen peroxide;

[0022] And / or, the concentration of inorganic acid in the treatment solution is 1 mol / L-5 mol / L, and the concentration of oxidant is 0.1 mol / L-0.5 mol / L.

[0023] In an optional embodiment, the solid content of the graphite slurry is 10%-30%;

[0024] And / or, the preparation process of the graphite slurry includes: mixing the second graphite material with water, and dispersing the particles in the slurry at a speed of 600 rpm to 1000 rpm for 30 min to 60 min.

[0025] In an optional embodiment, during the process of separating the graphite slurry to obtain the third graphite material, the stirring speed of the spiral centrifuge is controlled at 300rpm-600rpm and the centrifugation speed is controlled at 2500rpm-4500rpm. After centrifugation, the separated and purified graphite material is collected.

[0026] In an optional embodiment, the method further includes: mixing a third graphite material with a coating agent to obtain a mixture, and carbonizing the mixture.

[0027] The coating agent is selected from at least one of asphalt and phenolic resin.

[0028] In an optional embodiment, the third graphite material is dried and then mixed with the coating agent, and the mass ratio of graphite material to coating agent is controlled to be 100:(2-10);

[0029] And / or, during the mixing process with the coating agent, control the stirring speed to be 1000rpm-2000rpm and the mixing time to be 10min-30min;

[0030] And / or, the coating agent is asphalt, the particle size D50 of the asphalt is 2μm-6μm, and the softening point of the asphalt is 230℃-260℃;

[0031] And / or, the drying temperature of the third graphite material is 80℃-200℃, and the drying time is 10h-30h.

[0032] In an optional embodiment, during the carbonization process of the mixture, the carbonization temperature is controlled at 900℃-1400℃ and the holding time is 1h-5h.

[0033] And / or, control the heating rate to the carbonization temperature at a rate of 2℃ / min-5℃ / min.

[0034] The present invention has the following beneficial effects: The present invention proposes a combined treatment method of adding inorganic strong alkali or carbonate mixing - heat treatment - high pressure acid leaching - slurry preparation - spiral separation, which greatly reduces the ash impurity content in lithium-extracting graphite, and in particular can effectively remove impurities such as ZrO2 and TiO2 to obtain high-purity graphite.

[0035] In a preferred embodiment, the obtained high-purity graphite is mixed with a coating agent and then subjected to carbonization treatment to optimize the microstructure and specific surface area of ​​the graphite material, ultimately obtaining a high-purity, high-capacity, and high-efficiency lithium-ion battery anode graphite material. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 A schematic diagram of the spiral centrifugal separation of graphite and carbon black, and the amorphous carbon produced by pyrolysis and carbonization;

[0038] Figure 2 SEM image of recycled graphite. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0040] To address the problem of difficult removal of dopant elements in existing graphite waste recycling processes, this invention proposes a short, convenient, and rapid technical method to treat graphite waste after lithium extraction, achieving deep impurity removal and obtaining high-purity graphite that meets commercial requirements. Further, a coating method is employed to repair defects and restore the graphite structure, ultimately producing a high-performance anode graphite material that achieves a balance of purity, capacity, and initial efficiency. This solves the problem of difficult graphite waste recycling in this industry, enabling the resource utilization of industrial hazardous waste.

[0041] This invention provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, the steps of which are as follows:

[0042] S1, heat-treated with a mixture of inorganic strong alkali or carbonate.

[0043] Graphite waste is mixed with inorganic strong alkali or carbonate, and then heat-treated to convert impurities into salts that are easily removed by acid leaching, thus obtaining the first graphite material.

[0044] Specifically, by heat-treating graphite waste with a strong inorganic alkali or carbonate, ZrO2 and TiO2, which are difficult to remove by acid or alkali leaching, can be converted into zirconates and titanates. Zirconates and titanates are readily soluble in acids, facilitating the subsequent removal of Zr and Ti impurities by acid leaching. Simultaneously, the PVDF in the binder undergoes a defluorination reaction under the action of alkali or carbonate, accelerating the process and leading to pyrolysis and carbonization.

[0045] In some embodiments, the inorganic strong alkali is selected from at least one of sodium hydroxide and potassium hydroxide. The inorganic strong alkali can be any one or more of the above, and the mass ratio of graphite waste residue to the inorganic strong alkali is 100:(3-10), such as 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, 100:10, etc. The carbonate is selected from at least one of sodium carbonate and potassium carbonate. The carbonate can be any one or more of the above, and the mass ratio of graphite waste residue to carbonate is 100:(3-10), such as 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, 100:10, etc. Controlling the amount of inorganic strong alkali or carbonate within the above range enables ZrO2, TiO2, etc., in the graphite waste residue to be fully converted into acid-soluble salts, improving the impurity removal effect.

[0046] In some embodiments, during the preparation of the first graphite material, the heat treatment temperature is 800℃-1200℃, such as 800℃, 900℃, 1000℃, 1100℃, 1200℃, etc.; the holding time is 2h-10h, such as 2h, 3h, 5h, 8h, 10h, etc. The heat treatment temperature and time are preferably within the above range to ensure that ZrO2, TiO2, etc., in the graphite waste are fully converted into acid-soluble salts. The heat treatment process can be carried out under an inert atmosphere, the type of inert atmosphere is not limited, such as nitrogen, argon, etc.

[0047] In some embodiments, the graphite waste residue is first dried before being mixed with an inorganic strong alkali or carbonate to avoid the influence of impurities such as water on the surface of the graphite waste residue on the heat treatment. The drying temperature is 80℃-200℃, such as 80℃, 100℃, 130℃, 150℃, 180℃, 200℃, etc.; the drying time is 10h-30h, such as 10h, 15h, 20h, 25h, 30h, etc.

[0048] S2, High-pressure acid leaching

[0049] The first graphite material is mixed with a treatment solution containing inorganic acid and oxidant, and subjected to high-pressure acid leaching to remove impurity elements into the acid leaching solution. After solid-liquid separation, the second graphite material is obtained.

[0050] It should be noted that the high-pressure acid leaching provided in this embodiment of the invention has two functions: (1) High-pressure acid leaching increases the reaction kinetics of the acid leaching reaction, promotes the acid leaching efficiency and increases the impurity removal rate. After the above-mentioned alkali or carbonate heat treatment and high-pressure acid leaching combined treatment, graphite with ash content <0.1% was obtained. By optimizing the acid leaching conditions, high-purity graphite with ash content <0.05% can be obtained; (2) In high-pressure acid leaching, the residues of CMC (carboxymethyl cellulose), PVDF (polyvinylidene fluoride), and SBR (styrene-butadiene rubber) in graphite that have not been completely pyrolyzed will be hydrothermally carbonized under the action of high-pressure hydrothermal treatment, and transformed into fine amorphous carbon particles, which prepares for the removal of conductive carbon black and hydrothermally carbonized amorphous carbon particles in subsequent steps.

[0051] In some embodiments, during the preparation of the second graphite material, the high-pressure acid leaching reaction temperature is 110℃-180℃, the reaction pressure is 1MPa-2MPa, and the reaction time is 60min-36h. After maintaining the temperature and pressure, the temperature is lowered and the pressure is released before solid-liquid separation. By controlling the temperature, pressure, and time of acid leaching, the removal effect of impurities is improved, thereby increasing the purity of the graphite product. Specifically, the high-pressure acid leaching reaction temperature can be 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, etc.; the reaction pressure can be 1.0MPa, 1.3MPa, 1.5MPa, 1.8MPa, 2.0MPa, etc.; and the reaction time can be 60min, 3h, 5h, 8h, 10h, 15h, 20h, 25h, 30h, 36h, etc.

[0052] In some embodiments, the inorganic acid in the treatment solution is selected from at least one of sulfuric acid, hydrochloric acid, and nitric acid, and the inorganic acid can be any one or more of the above. Preferably, the inorganic acid in the treatment solution is a mixed acid, and the mixed acid includes sulfuric acid; that is, the inorganic acid is a mixed acid of sulfuric acid and hydrochloric acid, or a mixed acid of sulfuric acid and nitric acid. The oxidant in the treatment solution is hydrogen peroxide, but it is not limited to this; hydrogen peroxide is readily available and does not introduce impurities.

[0053] Furthermore, the concentration of inorganic acid in the treatment solution is 1 mol / L-5 mol / L, such as 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, etc.; the concentration of oxidant is 0.1 mol / L-0.5 mol / L, such as 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc.

[0054] S3, Pulping, Spiral Separation

[0055] The second graphite material is mixed with water to form a slurry, which is then passed through a screw centrifuge (such as a horizontal screw centrifuge) for centrifugal separation to obtain the third graphite material. This process, including screw centrifugation, yields a third graphite material. Figure 1 As shown, graphite particles can be separated to remove non-graphite carbon.

[0056] The graphite slurry has a solid content of 10%-30%, such as 10%, 15%, 20%, 25%, 30%, etc. The stirring speed of the screw centrifuge is controlled at 300rpm-600rpm, such as 300rpm, 400rpm, 500rpm, 600rpm, etc.; the centrifugation speed is controlled at 2500rpm-4500rpm, such as 2500rpm, 3000rpm, 3500rpm, 4000rpm, 4500rpm, etc. The centrifugation time is unlimited, using a simultaneous feeding and discharging method. After centrifugation, the separated and purified graphite material is collected.

[0057] It should be noted that this invention creatively proposes centrifugal separation of graphite slurry using a spiral centrifuge. By controlling the solid content and centrifugal speed of the prepared slurry, graphite and non-graphite carbon (conductive carbon black, CMC, PVDF, and amorphous carbon produced by SBR pyrolysis carbonization) are effectively separated from the graphite material. Additionally, some micro-powder in the graphite, due to its low specific gravity, also separates from the graphite, thus removing the micro-powder. By removing non-graphite carbon (amorphous carbon produced by conductive carbon black, CMC, PVDF, and SBR pyrolysis carbonization) and graphite micro-powder, the specific surface area and compaction density of the resulting graphite material can be increased. Since the presence of non-graphite carbon reduces the capacity of graphite as a negative electrode material in lithium-ion batteries, removing non-graphite carbon and graphite micro-powder can effectively improve the final capacity of the graphite.

[0058] Specifically, the horizontal spiral centrifuge is a commercially available device, such as the LW series model from Jiangsu Saideli Pharmaceutical Machinery Manufacturing Co., Ltd. A spiral centrifuge includes a mixer, a spiral separator, and a spiral conveyor.

[0059] like Figure 1As shown, graphite slurry is subjected to spiral separation in a horizontal screw centrifuge. Due to the density difference between the materials, water and graphite particles deposit on the drum wall and form precipitates. A screw conveyor rotates at a higher speed onto the drum and transports the graphite particles precipitated from the centrifuge. Simultaneously, a liquid level forms on the drum wall, the height of which is adjusted by an overflow weir. Most of the amorphous carbon produced by the pyrolysis and carbonization of conductive carbon black, CMC, PVDF, SBR, and other binders flows along with water, winding along the screw to the end of the cylindrical drum and the drain outlet. Because the carbon black particles and the amorphous carbon produced by pyrolysis and carbonization have very low content and much lower settling velocity compared to graphite, and because their density difference with water is small and their particle size is small, their residence time in water is long, making it insufficient for the centrifuge to deposit these particles on the drum wall. Therefore, the method provided in this embodiment of the invention can effectively separate graphite from conductive carbon black and the amorphous carbon produced by the pyrolysis and carbonization of binders in the slurry.

[0060] In actual operation, a peristaltic pump is used to supply graphite slurry from the container to the screw centrifuge, and the stirring system is controlled to stir the slurry in the container at a speed of 300-600 rpm. The centrifugal acceleration of the screw centrifuge is controlled, and the corresponding centrifugal speed is 2500-4500 rpm. After centrifugation, the separated and purified graphite is collected to obtain the third graphite material.

[0061] In some embodiments, the preparation process of the graphite slurry includes: mixing a second graphite material with water, and dispersing the particles in the slurry at a rotation speed of 600 rpm to 1000 rpm for 30 min to 60 min to ensure uniform particle distribution. Specifically, the slurry preparation can be carried out in a container of a three-bladed propeller agitator, and the stirring speed can be controlled to be 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, etc., and the stirring and dispersion time can be 30 min, 40 min, 50 min, 60 min, etc.

[0062] S4, Surface Coating

[0063] The third graphite material is mixed with a coating agent to obtain a mixture. The mixture is then carbonized and coated with asphalt or other coating agents to optimize the microstructure and specific surface area of ​​the graphite material, thereby improving the capacity and efficiency of the graphite.

[0064] In some embodiments, the coating agent is selected from at least one of asphalt and phenolic resin, and the coating agent can be any one or more of the above. Preferably, the coating agent is asphalt, the particle size D50 of the asphalt is 2μm-6μm, and the softening point of the asphalt is 230℃-260℃. Asphalt coating is beneficial to further improve the product's capacity and initial efficiency.

[0065] In some embodiments, the third graphite material is dried and then mixed with the coating agent, controlling the mass ratio of graphite material to coating agent to be 100:(2-10), such as 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, 100:10, etc. The amount of coating agent used is preferably within this range, which can effectively improve the capacity and initial efficiency of the graphite product. The drying temperature of the third graphite material is 80℃-200℃ (such as 80℃, 100℃, 150℃, 200℃, etc.), and the drying time is 10h-30h (such as 10h, 15h, 20h, 25h, 30h, etc.).

[0066] Furthermore, the mixing process with the coating agent can be carried out in a high-speed mixer, with the stirring speed controlled at 1000rpm-2000rpm, such as 1000rpm, 1500rpm, 2000rpm, etc.; the mixing time is 10min-30min, such as 10min, 20min, 30min, etc.

[0067] Furthermore, during the carbonization process of the mixture, the temperature is controlled to rise at a rate of 2℃ / min-5℃ / min to a carbonization temperature of 900℃-1400℃, and the holding time is controlled to be 1h-5h. Under these carbonization temperature and time conditions, more uniform coating can be achieved, improving the overall performance of the graphite product. Specifically, the heating rate can be 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, etc.; the carbonization temperature can be 900℃, 1000℃, 1100℃, 1200℃, 1300℃, 1400℃, etc.; and the holding time can be 1h, 2h, 3h, 4h, 5h, etc. After carbonization, the material is sieved and demagnetized to obtain high-purity, high-capacity, and high-efficiency lithium-ion battery anode graphite.

[0068] It should be noted that the regeneration and repair method provided in the embodiments of the present invention can effectively recover graphite and finally obtain high-purity (ash content <0.1%, or even <0.05%), high-capacity (capacity >350mAh / g), and high first-efficiency (first-efficiency >93%) lithium battery anode graphite material.

[0069] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0070] It should be noted that the preparation process of the graphite waste residue in the following embodiments and comparative examples is as follows: Waste lithium-ion batteries (ternary batteries recycled from other sources) are subjected to the following operations: 1. Waste lithium battery pretreatment: The waste batteries are crushed and sorted to remove the outer packaging, electrolyte, and electrode materials, resulting in battery black powder. 2. The battery black powder is placed in an acidic solution for acid leaching. Sulfuric acid or hydrochloric acid is typically used to dissolve the electrode materials and electrolyte, converting them into water-soluble salts. 3. Solution separation: After acid leaching, the solid waste residue is separated by methods such as pressure filtration or centrifugation (the water-soluble salt solution is used for subsequent precipitation, lithium extraction, and impurity removal). The resulting solid waste residue is the graphite waste residue, and the impurity composition of the residue is shown in Table 1.

[0071] Example 1

[0072] This embodiment provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, the steps of which are as follows:

[0073] (1) The graphite waste residue was dried at 120℃ for 12h to obtain the dried graphite waste residue; the dried graphite waste residue was added to 5% NaOH (i.e., the mass ratio of sodium hydroxide to graphite waste residue (the same below) is 5:100) and mixed evenly in a high-speed mixer. The mixing speed was 1500rpm and the mixing time was 15min.

[0074] (2) The graphite waste mixed with NaOH was heat-treated in an inert atmosphere (nitrogen, the same below) at a temperature of 950°C and a holding time of 6h to obtain the first graphite material.

[0075] (3) The first graphite material was poured into a treatment solution containing inorganic acid and hydrogen peroxide. The total concentration of inorganic acid in the treatment solution was 2 mol / L, and the inorganic acid was a mixture of sulfuric acid and hydrochloric acid with a molar ratio of 1:1. The concentration of hydrogen peroxide in the treatment solution was 0.2 mol / L. High-pressure acid leaching was carried out in the treatment solution. The liquid-to-solid ratio of acid leaching was 6 mL / g. The reaction temperature of high-pressure acid leaching was 180℃, the reaction pressure was 1.5-2.0 MPa, and the reaction time was 2 h. After maintaining the temperature and pressure, the temperature was lowered and the pressure was released. The solid and liquid were separated to obtain the second graphite material.

[0076] (4) The second graphite material is prepared into a slurry in a container of a three-bladed propeller agitator. The slurry is prepared with a solid content of 15%. The particles in the slurry are dispersed in the container at a speed of 1000 rpm for 30 min.

[0077] (5) The graphite slurry in the container is fed to the screw centrifuge by a peristaltic pump, and the stirring system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the screw centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After centrifugation, the third graphite material after separation and purification is collected.

[0078] (6) The third graphite material was dried at 120℃ for 12h to obtain dried high-purity graphite. The high-purity graphite and asphalt were mixed evenly in a high-speed mixer at a mass ratio of 100:3. The particle size of the asphalt was D50 = 2~3μm, the softening point of the asphalt was about 250℃, the speed of the high-speed mixer was 1500rpm, and the mixing time in the high-speed mixer was 15min.

[0079] (7) The mixture containing asphalt is carbonized in a carbonization furnace. The heating rate of the carbonization furnace is controlled at 2-5℃ / min, the carbonization holding temperature is 1200℃, and the carbonization holding time is 3h. After carbonization, the mixture is sieved and demagnetized to obtain high-purity, high-capacity, and high-efficiency lithium-ion battery negative electrode graphite.

[0080] The morphology of the recycled graphite product prepared in Example 1 is shown in the figure below. Figure 2 As shown, the graphite consists of blocky particles with a particle size of less than 50 μm. The graphite particles are uniform and have a relatively smooth surface.

[0081] Example 2

[0082] This embodiment provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, the steps of which are as follows:

[0083] (1) The graphite waste residue was dried at 120℃ for 12h to obtain the dried graphite waste residue; the dried graphite waste residue was added to 5% NaOH and mixed evenly in a high-speed mixer. The mixing speed was 1500rpm and the mixing time was 15min.

[0084] (2) The graphite waste mixed with NaOH was heat-treated under an inert atmosphere at a temperature of 950°C and a holding time of 6 hours to obtain the first graphite material.

[0085] (3) The first graphite material was poured into a treatment solution containing inorganic acid and hydrogen peroxide. The total concentration of inorganic acid in the treatment solution was 2 mol / L, and the inorganic acid was a mixture of sulfuric acid and hydrochloric acid with a molar ratio of 1:1. The concentration of hydrogen peroxide in the treatment solution was 0.2 mol / L. High-pressure acid leaching was carried out in the treatment solution. The liquid-to-solid ratio of acid leaching was 6 mL / g. The reaction temperature of high-pressure acid leaching was 160℃, the reaction pressure was 1.0-1.5 MPa, and the reaction time was 4 h. After maintaining the temperature and pressure, the temperature was lowered and the pressure was released. The solid and liquid were separated to obtain the second graphite material.

[0086] (4) The second graphite material is prepared into a slurry in a container of a three-bladed propeller agitator. The slurry is prepared with a solid content of 15%. The particles in the slurry are dispersed in the container at a speed of 1000 rpm for 30 min.

[0087] (5) The graphite slurry in the container is fed to the screw centrifuge by a peristaltic pump, and the stirring system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the screw centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After centrifugation, the third graphite material after separation and purification is collected.

[0088] (6) The third graphite material was dried at 120℃ for 12h to obtain dried high-purity graphite. The high-purity graphite and asphalt were mixed evenly in a high-speed mixer at a mass ratio of 100:3. The particle size of the asphalt was D50 = 2~3μm, the softening point of the asphalt was about 250℃, the speed of the high-speed mixer was 1500rpm, and the mixing time in the high-speed mixer was 15min.

[0089] (7) The mixture containing asphalt is carbonized in a carbonization furnace. The heating rate of the carbonization furnace is controlled at 2-5℃ / min, the carbonization holding temperature is 1200℃, and the carbonization holding time is 3h. After carbonization, the mixture is sieved and demagnetized to obtain high-purity, high-capacity, and high-efficiency lithium-ion battery negative electrode graphite.

[0090] Example 3

[0091] This embodiment provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, the steps of which are as follows:

[0092] (1) The graphite waste residue was dried at 120℃ for 12h to obtain the dried graphite waste residue; the dried graphite waste residue was added to 5% NaOH and mixed evenly in a high-speed mixer. The mixing speed was 1500rpm and the mixing time was 15min.

[0093] (2) The graphite waste mixed with NaOH was heat-treated under an inert atmosphere at a temperature of 950°C and a holding time of 6 hours to obtain the first graphite material.

[0094] (3) The first graphite material was poured into a treatment solution containing inorganic acid and hydrogen peroxide. The total concentration of inorganic acid in the treatment solution was 2 mol / L, and the inorganic acid was a mixture of sulfuric acid and hydrochloric acid with a molar ratio of 1:1. The concentration of hydrogen peroxide in the treatment solution was 0.2 mol / L. High-pressure acid leaching was carried out in the treatment solution. The liquid-to-solid ratio of acid leaching was 6 mL / g. The reaction temperature of high-pressure acid leaching was 180℃, the reaction pressure was 1.5-2.0 MPa, and the reaction time was 2 h. After maintaining the temperature and pressure, the temperature was lowered and the pressure was released. The solid and liquid were separated to obtain the second graphite material.

[0095] (4) The second graphite material is prepared into a slurry in a container of a three-bladed propeller agitator. The slurry is prepared with a solid content of 15%. The particles in the slurry are dispersed in the container at a speed of 1000 rpm for 30 min.

[0096] (5) The graphite slurry in the container is fed to the screw centrifuge by a peristaltic pump, and the stirring system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the screw centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After centrifugation, the third graphite material after separation and purification is collected.

[0097] (6) The third graphite material was dried at 120℃ for 12h to obtain dried high-purity graphite. The high-purity graphite and asphalt were mixed evenly in a high-speed mixer at a mass ratio of 100:3. The particle size of the asphalt was D50 = 2~3μm, the softening point of the asphalt was about 250℃, the speed of the high-speed mixer was 1500rpm, and the mixing time in the high-speed mixer was 15min.

[0098] (7) The mixture containing asphalt is carbonized in a carbonization furnace. The heating rate of the carbonization furnace is controlled at 2-5℃ / min, the carbonization holding temperature is 1100℃, and the carbonization holding time is 4h. After carbonization, the mixture is sieved and demagnetized to obtain high-purity, high-capacity, and high-efficiency lithium-ion battery negative electrode graphite.

[0099] Example 4

[0100] This embodiment provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, the steps of which are as follows:

[0101] (1) The graphite waste residue was dried at 120℃ for 12h to obtain the dried graphite waste residue; the dried graphite waste residue was added to 8% NaOH and mixed evenly in a high-speed mixer. The mixing speed was 1500rpm and the mixing time was 15min.

[0102] (2) The graphite waste mixed with NaOH was heat-treated under an inert atmosphere at a temperature of 950°C and a holding time of 6 hours to obtain the first graphite material.

[0103] (3) The first graphite material was poured into a treatment solution containing inorganic acid and hydrogen peroxide. The total concentration of inorganic acid in the treatment solution was 2 mol / L, and the inorganic acid was a mixture of sulfuric acid and hydrochloric acid with a molar ratio of 1:1. The concentration of hydrogen peroxide in the treatment solution was 0.2 mol / L. High-pressure acid leaching was carried out in the treatment solution. The liquid-to-solid ratio of acid leaching was 6 mL / g. The reaction temperature of high-pressure acid leaching was 180℃, the reaction pressure was 1.5-2 MPa, and the reaction time was 2 h. After maintaining the temperature and pressure, the temperature was lowered and the pressure was released. The solid and liquid were separated to obtain the second graphite material.

[0104] (4) The second graphite material is prepared into a slurry in a container of a three-bladed propeller agitator. The slurry is prepared with a solid content of 15%. The particles in the slurry are dispersed in the container at a speed of 1000 rpm for 30 min.

[0105] (5) The graphite slurry in the container is fed to the screw centrifuge by a peristaltic pump, and the stirring system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the screw centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After centrifugation, the third graphite material after separation and purification is collected.

[0106] (6) The third graphite material was dried at 120℃ for 12h to obtain dried high-purity graphite. The high-purity graphite and asphalt were mixed evenly in a high-speed mixer at a mass ratio of 100:3. The particle size of the asphalt was D50 = 2~3μm, the softening point of the asphalt was about 250℃, the speed of the high-speed mixer was 1500rpm, and the mixing time in the high-speed mixer was 15min.

[0107] (7) The mixture containing asphalt is carbonized in a carbonization furnace. The heating rate of the carbonization furnace is controlled at 2-5℃ / min, the carbonization holding temperature is 1200℃, and the carbonization holding time is 3h. After carbonization, the mixture is sieved and demagnetized to obtain high-purity, high-capacity, and high-efficiency lithium-ion battery negative electrode graphite.

[0108] Example 5

[0109] This embodiment provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, the steps of which are as follows:

[0110] (1) The graphite waste residue was dried at 120℃ for 12h to obtain the dried graphite waste residue; the dried graphite waste residue was added to 8% NaOH and mixed evenly in a high-speed mixer. The mixing speed was 1500rpm and the mixing time was 15min.

[0111] (2) The graphite waste mixed with NaOH was heat-treated under an inert atmosphere at a temperature of 950°C and a holding time of 6 hours to obtain the first graphite material.

[0112] (3) The first graphite material was poured into a treatment solution containing inorganic acid and hydrogen peroxide. The total concentration of inorganic acid in the treatment solution was 2 mol / L, and the inorganic acid was a mixture of sulfuric acid and hydrochloric acid with a molar ratio of 1:1. The concentration of hydrogen peroxide in the treatment solution was 0.2 mol / L. High-pressure acid leaching was carried out in the treatment solution. The liquid-to-solid ratio of acid leaching was 6 mL / g. The reaction temperature of high-pressure acid leaching was 160℃, the reaction pressure was 1.0-1.5 MPa, and the reaction time was 4 h. After maintaining the temperature and pressure, the temperature was lowered and the pressure was released. The solid and liquid were separated to obtain the second graphite material.

[0113] (4) The second graphite material is prepared into a slurry in a container of a three-bladed propeller agitator. The slurry is prepared with a solid content of 15%. The particles in the slurry are dispersed in the container at a speed of 1000 rpm for 30 min.

[0114] (5) The graphite slurry in the container is fed to the screw centrifuge by a peristaltic pump, and the stirring system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the screw centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After centrifugation, the third graphite material after separation and purification is collected.

[0115] (6) The third graphite material was dried at 120℃ for 12h to obtain dried high-purity graphite. The high-purity graphite and asphalt were mixed evenly in a high-speed mixer at a mass ratio of 100:3. The particle size of the asphalt was D50 = 2~3μm, the softening point of the asphalt was about 250℃, the speed of the high-speed mixer was 1500rpm, and the mixing time in the high-speed mixer was 15min.

[0116] (7) The mixture containing asphalt is carbonized in a carbonization furnace. The heating rate of the carbonization furnace is controlled at 2-5℃ / min, the carbonization holding temperature is 1200℃, and the carbonization holding time is 3h. After carbonization, the mixture is sieved and demagnetized to obtain high-purity, high-capacity, and high-efficiency lithium-ion battery negative electrode graphite.

[0117] Example 6

[0118] This embodiment provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, the steps of which are as follows:

[0119] (1) The graphite waste residue was dried at 120℃ for 12h to obtain the dried graphite waste residue; the dried graphite waste residue was added to 5% KOH and mixed evenly in a high-speed mixer. The mixing speed was 1500rpm and the mixing time was 15min.

[0120] (2) The graphite waste mixed with KOH was heat-treated under an inert atmosphere at a temperature of 950°C and a holding time of 6 hours to obtain the first graphite material.

[0121] (3) The first graphite material was poured into a treatment solution containing inorganic acid and hydrogen peroxide. The total concentration of inorganic acid in the treatment solution was 2 mol / L, and the inorganic acid was a mixture of sulfuric acid and hydrochloric acid with a molar ratio of 1:1. The concentration of hydrogen peroxide in the treatment solution was 0.2 mol / L. High-pressure acid leaching was carried out in the treatment solution. The liquid-to-solid ratio of acid leaching was 6 mL / g. The reaction temperature of high-pressure acid leaching was 180℃, the reaction pressure was 1.5-2.0 MPa, and the reaction time was 2 h. After maintaining the temperature and pressure, the temperature was lowered and the pressure was released. The solid and liquid were separated to obtain the second graphite material.

[0122] (4) The second graphite material is prepared into a slurry in a container of a three-bladed propeller agitator. The slurry is prepared with a solid content of 15%. The particles in the slurry are dispersed in the container at a speed of 1000 rpm for 30 min.

[0123] (5) The graphite slurry in the container is fed to the screw centrifuge by a peristaltic pump, and the stirring system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the screw centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After centrifugation, the third graphite material after separation and purification is collected.

[0124] (6) The third graphite material was dried at 120℃ for 12h to obtain dried high-purity graphite. The high-purity graphite and asphalt were mixed evenly in a high-speed mixer at a mass ratio of 100:3. The particle size of the asphalt was D50 = 2~3μm, the softening point of the asphalt was about 250℃, the speed of the high-speed mixer was 1500rpm, and the mixing time in the high-speed mixer was 15min.

[0125] (7) The mixture containing asphalt is carbonized in a carbonization furnace. The heating rate of the carbonization furnace is controlled at 2-5℃ / min, the carbonization holding temperature is 1200℃, and the carbonization holding time is 3h. After carbonization, the mixture is sieved and demagnetized to obtain high-purity, high-capacity, and high-efficiency lithium-ion battery negative electrode graphite.

[0126] Example 7

[0127] This embodiment provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, the steps of which are as follows:

[0128] (1) The graphite waste residue was dried at 120℃ for 12h to obtain the dried graphite waste residue; the dried graphite waste residue was added to 5% Na2CO3 and mixed evenly in a high-speed mixer. The mixing speed was 1500rpm and the mixing time was 15min.

[0129] (2) The graphite waste mixed with Na2CO3 was heat-treated under an inert atmosphere at a temperature of 900℃ and a holding time of 8h to obtain the first graphite material.

[0130] (3) The first graphite material was poured into a treatment solution containing inorganic acid and hydrogen peroxide. The total concentration of inorganic acid in the treatment solution was 2 mol / L, and the inorganic acid was a mixture of sulfuric acid and hydrochloric acid with a molar ratio of 1:1. The concentration of hydrogen peroxide in the treatment solution was 0.2 mol / L. High-pressure acid leaching was carried out in the treatment solution. The liquid-to-solid ratio of acid leaching was 6 mL / g. The reaction temperature of high-pressure acid leaching was 180℃, the reaction pressure was 1.5-2 MPa, and the reaction time was 2 h. After maintaining the temperature and pressure, the temperature was lowered and the pressure was released. The solid and liquid were separated to obtain the second graphite material.

[0131] (4) The second graphite material is prepared into a slurry in a container of a three-bladed propeller agitator. The slurry is prepared with a solid content of 15%. The particles in the slurry are dispersed in the container at a speed of 1000 rpm for 30 min.

[0132] (5) The graphite slurry in the container is fed to the screw centrifuge by a peristaltic pump, and the stirring system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the screw centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After centrifugation, the third graphite material after separation and purification is collected.

[0133] (6) The third graphite material was dried at 120℃ for 12h to obtain dried high-purity graphite. The high-purity graphite and asphalt were mixed evenly in a high-speed mixer at a mass ratio of 100:3. The particle size of the asphalt was D50 = 2~3μm, the softening point of the asphalt was about 250℃, the speed of the high-speed mixer was 1500rpm, and the mixing time in the high-speed mixer was 15min.

[0134] (7) The mixture containing asphalt is carbonized in a carbonization furnace. The heating rate of the carbonization furnace is controlled at 2-5℃ / min, the carbonization holding temperature is 1200℃, and the carbonization holding time is 3h. After carbonization, the mixture is sieved and demagnetized to obtain high-purity, high-capacity, and high-efficiency lithium-ion battery negative electrode graphite.

[0135] Example 8

[0136] This embodiment provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, the steps of which are as follows:

[0137] (1) The graphite waste residue was dried at 120℃ for 12h to obtain the dried graphite waste residue; the dried graphite waste residue was added to 5% K2CO3 and mixed evenly in a high-speed mixer. The mixing speed was 1500rpm and the mixing time was 15min.

[0138] (2) The graphite waste mixed with K2CO3 was heat-treated under an inert atmosphere at a temperature of 900℃ and a holding time of 8h to obtain the first graphite material.

[0139] (3) The first graphite material was poured into a treatment solution containing inorganic acid and hydrogen peroxide. The total concentration of inorganic acid in the treatment solution was 2 mol / L, and the inorganic acid was a mixture of sulfuric acid and hydrochloric acid with a molar ratio of 1:1. The concentration of hydrogen peroxide in the treatment solution was 0.2 mol / L. High-pressure acid leaching was carried out in the treatment solution. The liquid-to-solid ratio of acid leaching was 6 mL / g. The reaction temperature of high-pressure acid leaching was 180℃, the reaction pressure was 1.5-2 MPa, and the reaction time was 2 h. After maintaining the temperature and pressure, the temperature was lowered and the pressure was released. The solid and liquid were separated to obtain the second graphite material.

[0140] (4) The second graphite material is prepared into a slurry in a container of a three-bladed propeller agitator. The slurry is prepared with a solid content of 15%. The particles in the slurry are dispersed in the container at a speed of 1000 rpm for 30 min.

[0141] (5) The graphite slurry in the container is fed to the screw centrifuge by a peristaltic pump, and the stirring system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the screw centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After centrifugation, the third graphite material after separation and purification is collected.

[0142] (6) The third graphite material was dried at 120℃ for 12h to obtain dried high-purity graphite. The high-purity graphite and asphalt were mixed evenly in a high-speed mixer at a mass ratio of 100:3. The particle size of the asphalt was D50 = 2~3μm, the softening point of the asphalt was about 250℃, the speed of the high-speed mixer was 1500rpm, and the mixing time in the high-speed mixer was 15min.

[0143] (7) The mixture containing asphalt is carbonized in a carbonization furnace. The heating rate of the carbonization furnace is controlled at 2-5℃ / min, the carbonization holding temperature is 1200℃, and the carbonization holding time is 3h. After carbonization, the mixture is sieved and demagnetized to obtain high-purity, high-capacity, and high-efficiency lithium-ion battery negative electrode graphite.

[0144] Example 9

[0145] The only difference from Example 1 is that 3% sodium hydroxide is added in step (1).

[0146] Example 10

[0147] The only difference from Example 1 is that 8% sodium hydroxide is added in step (1).

[0148] Example 11

[0149] The only difference from Example 1 is that the heat treatment temperature in step (2) is 1150℃ and the holding time is 3.5h.

[0150] Example 12

[0151] The only difference from Example 1 is that the heat treatment temperature in step (2) is 1100℃ and the holding time is 4h.

[0152] Example 13

[0153] The only difference from Example 1 is that the acid leaching solution-to-solid ratio in step (3) is 8 mL / g.

[0154] Comparative Example 1

[0155] The main difference between Comparative Example 1 and Example 1 is that no strong inorganic base or carbonate is added in step (1), and the steps are as follows:

[0156] (1) The graphite waste residue was dried at 120℃ for 12h to obtain the dried graphite waste residue.

[0157] (2) The dried graphite waste residue was heat-treated in an inert atmosphere at a temperature of 950°C for 6 hours.

[0158] (3) The graphite waste residue after the above heat treatment was poured into a treatment solution containing inorganic acid and hydrogen peroxide. The total concentration of inorganic acid in the treatment solution was 2 mol / L, and the inorganic acid was a mixture of sulfuric acid and hydrochloric acid with a molar ratio of 1:1. The concentration of hydrogen peroxide in the treatment solution was 0.2 mol / L. High-pressure acid leaching was carried out in the treatment solution. The liquid-to-solid ratio of acid leaching was 6 mL / g. The reaction temperature of high-pressure acid leaching was 180℃, the reaction pressure was 1.5~2MPa, and the reaction time was 2h. After heat preservation and pressure holding, the temperature was lowered and the pressure was released. Solid-liquid separation was carried out to obtain graphite material A.

[0159] (4) The graphite material obtained by solid-liquid separation above is prepared into a slurry in a container of a three-bladed propeller agitator. The slurry is prepared with a solid content of 15%, and the particles in the slurry are dispersed in the container at a speed of 1000 rpm for 30 min.

[0160] (5) The graphite slurry in the container is fed to the screw centrifuge using a peristaltic pump, and the stirring system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the screw centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After centrifugation, the separated and purified graphite material B is collected.

[0161] (6) Graphite material B is dried at 120°C for 12 hours to obtain high-purity graphite. The high-purity graphite and a certain proportion of asphalt (the same proportion as in Example 1) are mixed evenly in a high-speed mixer. The particle size of the asphalt is D50 = 2-3 μm, the softening point of the asphalt is about 250°C, the speed of the high-speed mixer is 1500 rpm, and the mixing time in the high-speed mixer is 15 min.

[0162] (7) The mixture containing asphalt is carbonized in a carbonization furnace. The heating rate of the carbonization furnace is controlled at 2-5℃ / min, the carbonization holding temperature is 1200℃, and the carbonization holding time is 3h. After carbonization, the mixture is sieved and demagnetized to obtain the final graphite product.

[0163] Comparative Example 2

[0164] The main difference between Comparative Example 2 and Example 1 is that the heat treatment in step (2) is omitted, and high-pressure acid leaching is performed directly. The steps are as follows:

[0165] (1) The graphite waste residue was dried at 120℃ for 12h to obtain the dried graphite waste residue; the dried graphite waste residue was added to 5% NaOH and mixed evenly in a high-speed mixer. The mixing speed was 1500rpm and the mixing time was 15min.

[0166] (2) The graphite waste mixed with NaOH was poured into a treatment solution containing inorganic acid and hydrogen peroxide. The total concentration of inorganic acid in the treatment solution was 2 mol / L, and the inorganic acid was a mixture of sulfuric acid and hydrochloric acid with a molar ratio of 1:1. The concentration of hydrogen peroxide in the treatment solution was 0.2 mol / L. High-pressure acid leaching was carried out in the treatment solution. The liquid-to-solid ratio of acid leaching was 6 mL / g. The reaction temperature of high-pressure acid leaching was 180℃, the reaction pressure was 1.5~2MPa, and the reaction time was 2h. After maintaining the temperature and pressure, the temperature was lowered and the pressure was released. The solid and liquid were separated to obtain graphite material A.

[0167] (3) The graphite material obtained by solid-liquid separation above is prepared into a slurry in a container of a three-bladed propeller agitator. The slurry is prepared with a solid content of 15%, and the particles in the slurry are dispersed in the container at a speed of 1000 rpm for 30 min.

[0168] (4) The graphite slurry in the container is fed to the screw centrifuge using a peristaltic pump, and the stirring system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the screw centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After centrifugation, the separated and purified graphite material B is collected.

[0169] (5) Graphite material B is dried at 120℃ for 12h to obtain high-purity graphite. The high-purity graphite and a certain proportion of asphalt (the same proportion as in Example 1) are mixed evenly in a high-speed mixer. The particle size of the asphalt is D50 = 2~3μm, the softening point of the asphalt is about 250℃, the speed of the high-speed mixer is 1500rpm, and the mixing time in the high-speed mixer is 15min.

[0170] (6) The mixture containing asphalt is carbonized in a carbonization furnace. The heating rate of the carbonization furnace is controlled at 2-5℃ / min, the carbonization holding temperature is 1200℃, and the carbonization holding time is 3h. After carbonization, the mixture is sieved and demagnetized to obtain the final graphite product.

[0171] Comparative Example 3

[0172] The main difference between Comparative Example 3 and Example 1 is that steps (4) and (5) in Example 1 are not performed. The steps are as follows:

[0173] (1) The graphite waste residue was dried at 120℃ for 12h to obtain the dried graphite waste residue; the dried graphite waste residue was added to 5% NaOH and mixed evenly in a high-speed mixer. The mixing speed was 1500rpm and the mixing time was 15min.

[0174] (2) The graphite waste residue mixed with NaOH was heat-treated under an inert atmosphere at a temperature of 950℃ and a holding time of 6h.

[0175] (3) The graphite waste residue after the above heat treatment was poured into a treatment solution containing inorganic acid and hydrogen peroxide. The total concentration of inorganic acid in the treatment solution was 2 mol / L, and the inorganic acid was a mixture of sulfuric acid and hydrochloric acid with a molar ratio of 1:1. The concentration of hydrogen peroxide in the treatment solution was 0.2 mol / L. High-pressure acid leaching was carried out in the treatment solution. The liquid-to-solid ratio of acid leaching was 6 mL / g. The reaction temperature of high-pressure acid leaching was 180℃, the reaction pressure was 1.5-2.0 MPa, and the reaction time was 2 h. After heat preservation and pressure holding, the temperature was lowered and the pressure was released. Solid-liquid separation was carried out to obtain graphite material A.

[0176] (4) Graphite material A is dried at 120℃ for 12h to obtain high-purity graphite. The high-purity graphite and a certain proportion of asphalt (the same proportion as in Example 1) are mixed evenly in a high-speed mixer. The particle size of the asphalt is D50 = 2~3μm, the softening point of the asphalt is about 250℃, the speed of the high-speed mixer is 1500rpm, and the mixing time in the high-speed mixer is 15min.

[0177] (5) The mixture containing asphalt is carbonized in a carbonization furnace. The heating rate of the carbonization furnace is controlled at 2-5℃ / min, the carbonization holding temperature is 1200℃, and the carbonization holding time is 3h. After carbonization, the mixture is sieved and demagnetized to obtain the final graphite product.

[0178] Comparative Example 4

[0179] The main difference between Comparative Example 4 and Example 1 is that the high-pressure acid leaching treatment in step (3) of Example 1 is replaced by conventional acid leaching treatment, as follows:

[0180] (1) The graphite waste residue was dried at 120℃ for 12h to obtain the dried graphite waste residue; the dried graphite waste residue was added to 5% NaOH and mixed evenly in a high-speed mixer. The mixing speed was 1500rpm and the mixing time was 15min.

[0181] (2) The graphite waste residue mixed with NaOH was heat-treated under an inert atmosphere at a temperature of 950℃ and a holding time of 6h.

[0182] (3) The graphite waste residue after the above heat treatment was poured into a treatment solution containing inorganic acid and hydrogen peroxide. The total concentration of inorganic acid in the treatment solution was 2 mol / L, and the inorganic acid was a mixture of sulfuric acid and hydrochloric acid with a molar ratio of 1:1. The concentration of hydrogen peroxide in the treatment solution was 0.2 mol / L. Conventional acid leaching was carried out in the treatment solution. The liquid-to-solid ratio of acid leaching was 6 mL / g, the reaction temperature of acid leaching was 80℃, and the reaction time was 24 h. Graphite material A was obtained by solid-liquid separation.

[0183] (4) The graphite material obtained by solid-liquid separation above is prepared into a slurry in a container of a three-bladed propeller agitator. The slurry is prepared with a solid content of 15%, and the particles in the slurry are dispersed in the container at a speed of 1000 rpm for 30 min.

[0184] (5) The graphite slurry in the container is fed to the screw centrifuge using a peristaltic pump, and the stirring system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the screw centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After centrifugation, the separated and purified graphite material B is collected.

[0185] (6) Graphite material B is dried at 120°C for 12 hours to obtain high-purity graphite. The high-purity graphite and a certain proportion of asphalt (the same proportion as in Example 1) are mixed evenly in a high-speed mixer. The particle size of the asphalt is D50 = 2-3 μm, the softening point of the asphalt is about 250°C, the speed of the high-speed mixer is 1500 rpm, and the mixing time in the high-speed mixer is 15 min.

[0186] (7) The mixture containing asphalt is carbonized in a carbonization furnace. The heating rate of the carbonization furnace is controlled at 2-5℃ / min, the carbonization holding temperature is 1200℃, and the carbonization holding time is 3h. After carbonization, the mixture is sieved and demagnetized to obtain the final graphite product.

[0187] Comparative Example 5

[0188] The main difference between Comparative Example 5 and Example 1 is that Comparative Example 5 does not involve coating with asphalt, and the steps are as follows:

[0189] (1) The graphite waste residue was dried at 120℃ for 12h to obtain the dried graphite waste residue; the dried graphite waste residue was added to 5% NaOH and mixed evenly in a high-speed mixer. The mixing speed was 1500rpm and the mixing time was 15min.

[0190] (2) The graphite waste residue mixed with NaOH was heat-treated under an inert atmosphere at a temperature of 950℃ and a holding time of 6h.

[0191] (3) The graphite waste residue after the above heat treatment was poured into a treatment solution containing inorganic acid and hydrogen peroxide. The total concentration of inorganic acid in the treatment solution was 2 mol / L, and the inorganic acid was a mixture of sulfuric acid and hydrochloric acid with a molar ratio of 1:1. The concentration of hydrogen peroxide in the treatment solution was 0.2 mol / L. High-pressure acid leaching was carried out in the treatment solution. The liquid-to-solid ratio of acid leaching was 6 mL / g. The reaction temperature of high-pressure acid leaching was 180℃, the reaction pressure was 1.5-2.0 MPa, and the reaction time was 2 h. After heat preservation and pressure holding, the temperature was lowered and the pressure was released. Solid-liquid separation was carried out to obtain graphite material A.

[0192] (4) The graphite material obtained by solid-liquid separation above is prepared into a slurry in a container of a three-bladed propeller agitator. The slurry is prepared with a solid content of 15%, and the particles in the slurry are dispersed in the container at a speed of 1000 rpm for 30 min.

[0193] (5) The graphite slurry in the container is fed to the screw centrifuge using a peristaltic pump, and the stirring system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the screw centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After centrifugation, the separated and purified graphite material B is collected.

[0194] (6) The purified graphite material B is subjected to heat treatment. The heating rate of the carbonization furnace is controlled at 2-5℃ / min, the carbonization holding temperature is 1200℃, and the carbonization holding time is 3h. After carbonization, the graphite product is obtained by sieving and demagnetizing.

[0195] Experimental Example 1

[0196] The physicochemical properties of the graphite products prepared in the test examples and comparative examples are as follows:

[0197] Table 1 compares the impurity element content of Examples 1-13 with that of Comparative Examples 1-5:

[0198] Table 1. Graphite impurity element content (ppm)

[0199]

[0200]

[0201] Table 2 shows the test results of tap density, ash content, and specific surface area of ​​the finished graphite products from Examples 1-13 and Comparative Examples 1-5:

[0202] Table 2. Tap density, ash content, and specific surface area of ​​finished graphite products.

[0203]

[0204]

[0205] The cells were assembled into coin cells for electrical performance testing. Test conditions: test voltage 0–2V, constant current charge / discharge, rate of 0.1C. Table 3 compares the initial delithiation specific capacity and coulombic efficiency of the graphite samples prepared in Examples 1-13 and Comparative Examples 1-5.

[0206] Table 3. Delithiation specific capacity and coulombic efficiency test data of graphite samples.

[0207] sample <![CDATA[Specific delithiation capacity (mAh g -1 )]]> Coulomb efficiency (%) Example 1 351.12 93.3 Example 2 351.46 93.2 Example 3 352.01 93.4 Example 4 351.43 93.2 Example 5 351.08 93.3 Example 6 350.93 93.3 Example 7 351.54 93.2 Example 8 351.45 93.3 Example 9 351.49 93.3 Example 10 351.58 93.4 Example 11 352.12 93.4 Example 12 351.69 93.3 Example 13 352.10 93.5 Comparative Example 1 343.67 90.6 Comparative Example 2 342.58 89.8 Comparative Example 3 349.56 92.4 Comparative Example 4 350.25 92.5 Comparative Example 5 352.16 92.1

[0208] The results show that the impurity elements and ash content of the Examples and Comparative Examples 1, 2, and 4 are much lower. Although the levels of impurity elements and ash content are similar between the Examples and Comparative Example 3, Comparative Example 3 exhibits a higher specific surface area because it did not separate carbon black and amorphous carbon by centrifugation. Although the levels of impurity elements and ash content are similar between the Examples and Comparative Example 5, Comparative Example 5 exhibits a higher specific surface area because it did not undergo asphalt coating treatment and the defects were not fully repaired.

[0209] Therefore, the graphite products prepared in the embodiments of the present invention have lower ash content, higher tap density, and lower specific surface area; and the ash content of the embodiments after reducing impurities, removing carbon black, and removing amorphous carbon reaches that of battery-grade graphite, and the electrical performance is excellent.

[0210] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for regenerating and remediating graphite waste residue after wet lithium extraction from waste lithium batteries, characterized in that, include: The graphite waste residue is mixed with an inorganic strong alkali or carbonate, and then subjected to heat treatment to obtain the first graphite material. The carbonate is selected from at least one of sodium carbonate and potassium carbonate; The first graphite material is mixed with a treatment solution containing inorganic acid and oxidant, subjected to high-pressure acid leaching, and then separated into solid and liquid components to obtain the second graphite material. The second graphite material is mixed with water to form a slurry, thus obtaining a graphite slurry. The graphite slurry is fed into a horizontal screw centrifuge for centrifugal separation to obtain a third graphite material.

2. The regeneration and repair method according to claim 1, characterized in that, During the preparation of the first graphite material, the heat treatment temperature is 800℃-1200℃, and the holding time is 2h-10h. And / or, heat treatment is performed under an inert atmosphere.

3. The regeneration and repair method according to claim 1 or 2, characterized in that, The inorganic strong alkali is selected from at least one of sodium hydroxide and potassium hydroxide, and the mass ratio of the graphite waste residue to the inorganic strong alkali is 100:(3-10). And / or, the mass ratio of the graphite waste residue to the carbonate is 100:(3-10). And / or, the graphite waste residue is first dried and then mixed with an inorganic strong alkali or carbonate, with the drying temperature controlled at 80℃-200℃ and the drying time at 10h-30h.

4. The regeneration and repair method according to claim 1, characterized in that, In the process of preparing the second graphite material, the reaction temperature of the high-pressure acid leaching is 110℃-180℃, the reaction pressure is 1MPa-2MPa, and the reaction time is 60min-36h. After that, the temperature is reduced and the pressure is released before solid-liquid separation is carried out. And / or, the inorganic acid in the treatment solution is selected from at least one of sulfuric acid, hydrochloric acid, and nitric acid.

5. The regeneration and repair method according to claim 4, characterized in that, The inorganic acid in the treatment solution is a mixed acid, and the mixed acid includes sulfuric acid; And / or, the oxidant in the treatment solution is hydrogen peroxide; And / or, the concentration of inorganic acid in the treatment solution is 1 mol / L-5 mol / L, and the concentration of oxidant is 0.1 mol / L-0.5 mol / L.

6. The regeneration and repair method according to claim 1, characterized in that, The solid content of the graphite slurry is 10%-30%; And / or, the preparation process of the graphite slurry includes: mixing the second graphite material with water, and dispersing the particles in the slurry at a speed of 600 rpm to 1000 rpm for 30 min to 60 min.

7. The regeneration and repair method according to claim 1, characterized in that, In the process of separating the graphite slurry to obtain the third graphite material, the stirring speed of the horizontal screw centrifuge is controlled at 300rpm-600rpm and the centrifugation speed is controlled at 2500rpm-4500rpm. After centrifugation, the separated and purified graphite material is collected.

8. The regeneration and repair method according to claim 1, characterized in that, Also includes: The third graphite material is mixed with a coating agent to obtain a mixture, and the mixture is then carbonized. The coating agent is selected from at least one of asphalt and phenolic resin.

9. The regeneration and repair method according to claim 8, characterized in that, The third graphite material is dried and then mixed with the coating agent, and the mass ratio of graphite material to coating agent is controlled to be 100:(2-10). And / or, during the mixing process with the coating agent, the stirring speed is controlled at 1000rpm-2000rpm and the mixing time is 10min-30min; And / or, the coating agent is asphalt, the particle size D50 of the asphalt is 2μm-6μm, and the softening point of the asphalt is 230℃-260℃; And / or, the drying temperature of the third graphite material is 80℃-200℃, and the drying time is 10h-30h.

10. The regeneration and repair method according to claim 8, characterized in that, During the carbonization process of the mixture, the carbonization temperature is controlled at 900℃-1400℃ and the holding time is 1h-5h. And / or, control the heating rate to the carbonization temperature at a rate of 2℃ / min-5℃ / min.

Images